(1) Field of the Invention
The present invention relates to a multiwindow display control method and apparatus to control a multiwindow display.
A multiwindow display provides an environment in which a plurality of windows are displayed on a single screen, whereby users can efficiently carry out various jobs at the same time. The multiwindow display has become essential in the construction of a human-computer interface, such as a work station.
(2) Description of the Related Art
In a conventional multiwindow display, a technique is required by which the required functions of a high speed display and high degree of freedom in displaying the multiwindow display are obtained.
Therefore, in a conventional multiwindow system, a plurality of frame memories each of the same size as a display screen are provided, or a single frame memory having a size larger than the display screen is provided. In the former case, each frame memory stores pixel data of a single window, and in the latter case, the larger size frame memory stores pixel data of a plurality of windows. In both cases, to combine the pixel data of the windows, conventional hardware is used to directly synthesize or combine the pixel data of each window in the frame memory, to thereby obtain a multiwindow display screen image which is displayed on a display screen.
For example, assuming that pixel data of the respective windows are stored in different locations in the larger size frame memory, and that window display control data such as storing location, display point, overlapping priority and so forth are set in a controller. Then, the hardware displays the windows on the display screen, based on the window display control data, by switching the reading location from the frame memory synchronously with the display timing.
Therefore, in the conventional hardware window system, it is necessary only to set necessary window display control data corresponding to the respective windows in the controller, and thus there is advantageously obtained a high speed display switching capability.
Accordingly, basic operations such as the generating/erasing of a window, movement of a window, change of an overlapping of the windows, or a change of the size of a window, can be carried out by the above mentioned conventional example, but it is difficult to manage the plurality of windows as a single group window in a convenient, efficient manner.
Because of the high degree amount of human interface or interaction in recent years, there is a need to provide a high degree of freedom of operation which simulates the human interaction by which a linking among a plurality of windows, such as a page movement or page turning operation, can be obtained. Note, in this case, each page constitutes a group of windows including a plurality of windows.
To realize such a high degree of freedom of operation such as a page turning operation or a page movement, overlapping display control is necessary, and in such an overlapping display, a plurality of groups of windows are simultaneously displayed on a screen.
Conventionally, the overlapping display control is carried out using a single variable, i.e., a priority of each window with respect to the display order is used regardless of the group of windows to which the windows belong, and therefore, it is very difficult to carry out an overlapping display of the groups of windows. Namely, in the conventional technique for effecting the overlapping display control of the group windows, the load on software is very heavy and thus the advantage of a satisfactory high speed display by hardware cannot be obtained. A group of windows is also hereinafter referred to as a group window.
As described above, in the conventional example, a problem arises in the complexity of the operations for controlling change of a display of a plurality of groups of windows each including a plurality of windows.